Relay control circuit



' Oct. 23, 1945. w, E SMPSON 2,387,536

RELAY CONTROL CIRCUIT Filed Sept; 28, 1942 DEV/CE Facomm? vfm ATTORNEY Patented Oct. 23,, 1945 RELAY CONTROL CIRCUIT William E. Simpson, South Ozone Park, N. Y., as-

signor to Radio Corporation of America, a corporation of Delaware Application September 28, 1942, Serial No. 459,953

6 Claims.

This invention relates to relay control circuits and more particularly to a device for reversing the direction of current in a relay coil or in any desired responsive device, such as a signal recorder.

In carrying out my invention I have endeavored to provide a simple form of push-pull circuit which is operable at relatively high speed for translating telegraph signals and the like. I have found, however, that the invention has other uses.

Accordingly, it is an object of my invention to provide a relay control circuit which requires the minimum of electronic equipment for operation in a push-pull manner.

It i another object of my invention to provide electronic means of the simplest, type in combination with a polarized relay such that the relay may be rendered reversibly operable in response to the reception of on-and-oif signals.

It is still another object of my invention to provide a keying device operable upon a polarized re lay or other responsive means so as to produce effects equivalent to those of a push-pull circuit, even though the keying circuit is merely one which is alternately opened and closed.

Other objects and advantages of my invention will be made apparent in the description to fol low. This description is accompanied by a drawing, in which:

Fig. 1 shows diagrammatically a preferred circuit arrangement including an electronic device and a polarized relay for carrying out the invention;

Fig. 2 shows a modified form of my invention in which a simple telegraph key is utilized to vary the direction of current flow through the circuit of a responsive device; and

Fig. 3 shows a third embodiment of the invention in which the reversal of current through the circuit of a signal recorder is accomplished by the keying of an electronic control means, the latter being supplied with potentials from a two-section direct current source having a grounded mid-tap.

In an illustrative application of my invention, a. negative voltage is used as the marking voltage from a rectifier which receives telegraphic tone signals. The negative voltage output from such a. rectifier is applied to a control grid in an electron discharge tube thereby to block this tube and to provide a path of current flow in one direction through the winding of a polarized relay. When the signal terminates so that no rectification takes place, then the controlled electron tube becomes conductive and permits flow of current in the opposite direction through the winding of the aforementioned polarized relay. This operation will be better understood after describing the circuits of the several figures in detail.

Referring to Fig. 1, I show therein a transformer I having a primary winding connected to the input terminals A-A. The secondary of this transformer has its terminals connected to the anodes 3 in a full wave rectifier tube 2. A midtap on the secondary winding of transformer I is connected to the control grid 6 in a discharge tube 4. The common cathode 5 in the rectifier tube 2 is grounded.

Tube 4 may be a triode discharge tube as shown, or it may have additional electrodes if desired. The control grid 6 is preferably provided with a grid leak resistor 1 of a relatively low ohmic value, say 3000 ohms, for example.

A direct current source 8 is grounded at the negative terminal thereof and its positive terminal is connected to a voltage divider having two sections 9 and I0. Section 9 is in the form of an adjustable potentiometer, the movable tap ll whereof is connected to the anode 12 in the discharge tube 4. The cathode I3 of this tube is in circuit with the winding M of a polarized relay. This relay winding, therefore, completes the tube circuit; to ground and to the negative terminal of the source 8.

In Fig. 1 the dotted line enclosure 15 represents any desired utilization device, although it is shown to include, for example, a polarized relay having a winding [4 and an armature 16. This armature is enabled to complete either of two circuits, namely, from terminal B to terminal C, or from terminal B to terminal D, depending upon the position which the armature l6 occupies.

Upon reception of an incoming signal, rectification takes place in the tube 2. A negative voltage is derived from the center-tap on the secondary winding of the transformer I which is applied across resistor 1 and through the relay winding I4 to ground. The cathode 5 in the rectifier tube 2 is held at ground potential and the grid 6 in tube 4 becomes so negatively biased that tube 4 becomes blocked. Under these conditions the right hand terminal of coil I4 is more positive than the left hand terminal, and current flows in the proper direction for positioning the armature 16 against contact C.

Upon cessation of the signal, rectification of energy no longer occurs in tube 2 and hence the resistor 1 ceases to draw current. Tube 4 becomes conductive and the flow of current therein from the positive terminal of source 8 is such as to render the cathode I3 considerably positive with respect to ground. This current, therefore, traverses the coil Id in the opposite direction from that which existed during the rectification of a tone signal. Under these conditions, the armature I6 is moved to the right and into engagement with the contact D.-

A significant feature of the circuit arrangement shown in Fig. I resides in the ohmic value assigned to the resistor This value is preferably made such that current of the same amplitude will flow through the relay coil It in either direction, depending upo'n the conductive or blocking condition'of tube 4. A refinement of adjustment for equalizing the currents of opposite polarity may also be obtained by proper setting of the tap II on the potentiometer 9 so as to suitably fix the operating voltage applied to the anode l2 in tube It should be particularly noted that the relay winding It is connected in a common portion of a branched circuit, and that the direction of the current traversing the winding depends upon which one of the circuit branches is rendered conductive at any given instant.

I have found th'at'the circuit arrangement of Figjl is relatively free from operational failure due to variations in the amplitude of the received signal. The dependable action is due to the fact that the tube may be biased to cut-off by a relatively weak signal, and furthermore, if desired, the relay may be biased by a spring or a bias coil, so as to aid the magnetizing force of the rectified, signal current in coil I4. Stronger signals would only intensify this current and would merely hasten the throw of the armature l6 toward contact C. Then again, when the spacing signal condition exists, the current amplitude in the opposite direction through th coil Hi in series with the space path of tube l is made entirely dependent upon the chosen setting of thetap on the potentiometer 9.

It is-well known that printer code signals, when transmitted over long lines or radio channels,

are subject to considerable distortion, and usually require re-shapin'g before theycan be used to control a "teletype printer or its equivalent.

I have found that the adjustments of the reshaping circuit characteristicsare much less crit-' ical when using my invention than otherwise.

Referring to Fig. 2, I show an alternative embodiment in which a key 2| is used to control the responsive device la. In this case the source 8 has its positive terminal directly connected to the anodez|2 in tubee. The negative terminal of the source 8 is connected to one contact of key 2|. Connected. across the two terminals of source 8 is a voltage divider consisting of two sections 22 and 23. Th junction between sections 22 and 23 is grounded, thusproviding a ground potential intermediate between the terminals of the source 8.

The responsive device |5a is constituted as a load between the cathode I3 in tube 5 and ground;

In the operation of the circuit arrangement of Fig. 2. the closing of key 2| places a strongly negativebias upon the grid in tube 6, since that gridi's directly connected to the negative terminal of the source 8 and a potential drop exists in resistor 7 due to the flow of current through the responsive device |5a from the more positive ground potential. Tube l is, therefore, blocked under this condition.

When the key 2| is open-circuited, then the potential drop in the grid resistor is reduced substantially to Zero value and the. tube t is thus rendered conductive. Current, therefore, flows through tube 5 from the positive terminal of source 8, through the tube, from the cathode |3 through the responsive device l5a, through ground, and thence through the potentiometer section 22 to the negative terminal of source 8. This current through responsive device |5a is in the reverse direction from that which was maintained during the closure of key 2|. The ohmic value of the resistor I can be so chosen as to-provide an equal fiow of current through the responsive device |5a in opposite directions.

Referring now to Fig. 3, the embodiment therein shown differs only slightly from that of the circuit arrangement of Fig. 2. One feature of diilerence resides in the elimination of the potentiometer sections 22 and 23, a divided source 8a and 8b being utilized with a grounded junction therebetween.

In certain instances it may be desirable to provide a relatively high impedance grid biasing resistor 31. For purposes of illustration, it is indicated as having a value of .5 megohm. Ordinarily this would be too high a resistance for the conductance of operating current through the signal recorder |5b. Hence a shunt circuit comprising resistor 38 is connected between the cathode l3 and the negative terminal of source 8b.

One contact on the key 2| is connected to the grid 6 in tube 6 and the other contact is connected to the negative terminal of source 8b. The signal recorder.circuit within the unit l5b is constituted as a useful load when tube 4 is rendered conductive and operating potentials are derived from section Ba of the direct current source.

When the key 2| is closed, a negative bias is applied to the grid 6 from the negative terminal of source 81), and tube 4 becomes blocked. Un-

der this condition a potential drop exists in re--' sistors 31 and 38 and current flows from ground through the signal recorder and through resistor 38 to the negative terminal in the direct current source section 812. It will thus be seen that the current is caused to flow reversibly through the signal recorder |5b in response to the manipulation of the key 2| when closing and opening the same.

It will be clear to those skilled in the art that other modifications of my invention may be made without departing from the spirit of the invention. The claims are, therefore, intended to be of such scope as to include not only the specific embodiments shown and described, but others as well.

I claim:

l. The method of reversibly actuating an electrically responsive device by direct currents of opposite polarity, one of said currents being derived from a constantly present source and the second of said currents being a rectification prodnot which exists only in the presence of a signal potential, said method comprising the steps of causing a current from said source to traverse said device in series with the path of an electron discharge, causing the second current when it exists to traverse said device in series with an impedance path, and causing said electron discharge to be blocked by a cut-off bias which results from the potential drop across said i'mpedance during the existence of the second current.

2. In an electronic switching system for reverstube, where such states result from the absence and presence respectively of an incoming signal potential, the method of producing such current reversals which comprises utilizing the space path nections with a utilization device, said switch cornprising a triode discharge tube having its cathode connected through said utilization device to ground, a source of direct current connected in circuit between the anode of said tube and ground, an impedance connected between the cathode and the control grid of said tube, and means including an intermittent grid biasing source derived from rectified signal potential and connected in circuit with said impedance and said utilization device for performing the dual function of blocking said tube and reversing the polarity of the current traversing said utilization device in relation to the current traversing the same when said tube is conductive.

4. In a device of the class described, a polarized relay having a winding in the common portion of a branched circuit, one of the circuit branches including a source of direct current and the space path of an electron discharge tube, the other of the circuit branches including a signal energy source and an input circuit impedance, said impedance being connected between a cathode and a control grid in said tube, said tube being conductive in the absence of signal ener y. and rectifying means effective to apply said signal energy as a cut-off bias potential across said input circuit impedance while polarizing said relay winding in a direction opposite to its polarization when energized by current through said space path.

5. The combination according to claim 4 and including potentiometer means for adjusting the potential drop across said space path, thereby to predetermine the ratio between current amplitudes of opposite polarity in said relay winding.

6. In apparatus of the class described, a device capable of two opposite responses in dependence upon the direction of current which it is arranged to conduct, two branch circuits connected to one terminal of said device, the other terminal thereof being grounded, one of said branch circuits including a constant current source and the space path of a controllable discharge tube, the other of said branches including an intermittent current source of the type having means for rectifying a signal potential and an input circuit impedance connected between a cathode and a control grid in said tube, said sources being arranged to feed direct current in opposite directions through the circuit of said device, and means effective in the presence of current flow from said intermittent source for blocking the discharge in said tube.

WILLIAM E. SIMPSON. 

